Conformity Magazine - June 2008 - (Page 22)

ESD Open Forum ESD Stressing of Devices and Components Provided by the ESD Association The short answer to this question is no. IEC 61000-4-2 was expressly developed to test ESD robustness of consumer products in the field. However, OEMs have begun asking IC and component manufacturers to supply IEC test results to give them some level of confidence that the exposed pins will meet the specified IEC requirements in the final system. The IEC standard does not specify the test conditions for stressing an integrated circuit or a component. Questions such as how the IC should be mounted during the test, how the IC should be grounded, how the ESD gun’s ground should be connected, and pin combinations to stress are not addressed in the IEC standard because the standard is not intended for the testing of components. Without detailed specifications for the testing of a component, there are too many variables left to the test engineer. Test results, even from very qualified test engineers, are likely to vary widely between different testing laboratories. Q: A: Should I be using the IEC 61000-4-2 test to characterize devices or components? In the HMM test, the full IEC waveform stress is delivered to the IC. In a system test, the amount of the stress current and the wave shape will vary depending on the system design. Thus, differences between the HMM and final system IEC results are still expected. However, using the HMM test as a common test method does allow comparison of results for particular devices from different suppliers. At the ESD Association, we are developing a Standard Practice document defining the Human Metal Model (HMM) test in the Working Group 5.6. The same IEC waveform is used for this testing procedure as is used in the IEC 61000-4-2 test. However, the test bench is different. The IEC system test setup consists of a wood table on a metal ground plane. A metallic horizontal coupling plane (HCP) and an insulator cover the table. The system under test is placed on the table. One of the main changes that will probably be done for HMM testing is the removal of the coupling planes and their associated capacitances. While this is expected to deliver a more severe current waveform to the DUT, it means that all HMM testing will follow a Standard Practice. 22 Conformity JUnE 2008 Q: A: So what tests should be used to give customers some degree of confidence in their system level test results? The HMM test procedure is specified for contact discharge testing only. Indeed, air discharge testing should not be done on devices outside the final system. The results from air discharge testing are almost completely dominated by such factors as shielding in the final system, grounding of the circuit boards in the system, and even the system packaging itself. Since none of these factors can be controlled by the device manufacturer, any results from air discharge testing would be meaningless for the final system. Consequently, air discharge test results from devices would either provide the customer with a false sense of security, or send the supplier on a costly quest for ESD protection that would likely be superfluous or ineffective. Q: A: Can the HMM test method be used for air discharge, or is it intended for contact discharge only?

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Conformity - June 2008 Contents Editor's Note 700 MHz Auction Raises a Record $20 Billion FCC Modifies PCS and AWS Power Limit Rules for Broadband Wireless Commission Designates Spectrum Test Bed FCC Releases Report on Wireless Competition Commission Proposes $5 Million Fine for Slamming Using EDX for Non-Destructive Detection of Lead in Consumer Products ESD Open Forum Challenges in Testing - Improving Election Security and Accuracy Part 1 Challenges in Testing - Human Body Model: The Hidden Challenges High-Speed Signal Integrity Considerations for ESD Components Focus On...EMC Components Buyer's Guide FCC Levies $2.6 Million Fine for Junk Faxes FDA Updates Guidance on its Product Review Process EU Issues Updated Energy Star Regulations EU Repeals Directive on Veterinary Electro-Medical Equipment New Product Announcements Updated Standards List for the EU's PPE Directive CPSC Announces New Effort to Keep Out Hazardous Products CPSC Actions in the News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity - June 2008

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